Apparatus and method for sanitizing tableware



April 25, 1961 E. s. STODDARD 2,

APPARATUS AND METHOD FOR SANITIZING TABLEWARE Filed Oct. 25, 1957 2 Sheets-Sheet 1 I I l INVENTOR. EDGAR S. STODDARD ATTORNEY April 25, 1961 E. s. STODDARD 2,981,267

APPARATUS AND METHOD FOR SANITIZING TABLEWARE Filed Oct. 25, 1957 2 Shees-Sheet 2 INVENTOR. EDGAR S. STODDARD BZLLMAAMQ/ ATTORNEY 2,981,257 Patented Apr. 25, 196i,

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APPARATUS AND METHOD FOR SANITIZING TABLEWARE Edgar 3. Stoddard, Oak Park, 121., assignor to General Electric Company, a corporation of New York Filed Oct. 25, 1957, Ser. No. 692,441

Claims. (Cl. 134-=-95) This invention relates to apparatus and a method for sanitizing tableware and more particularly it relates to the use of an improved storage rack having properties which are effective to sanitize tableware or other articles subject to contamination by micro-organisms. The rack embodying my invention may be used in a dish washing machine, or in a storage cabinet such as the ordinary kitchen cabinet.

Articles of tableware such as dishes, cups, glasses, and silverware are in use at least three times daily in the average home. After each usage the tableware must be made clean and sanitary for re-use. The cleaning operation ideally should remove all food soils and pathogenic micro-organisms from the tableware articles so as to make them sterile. However, it is generally recognized that this does not usually occur with commonly used dish washing methods. Even the modern household electric dish washing machine will not consistently make tableware absolutely sterile, although it does a better and more uniformly sanitary job of dish washing than can be done by hand (Mallman, W.L., Hand Versus Machine Dishwasher in the Home, ber 1955). It is well known that tableware in daily use may become contaminated with harmful live bacteria and viruses; if these micro-organisms, which may include influenza virus, streptococcus and tuberculosis bacteria are not'removed from tableware during washing operations, they may infect the next user (see Lynch, Charles, and Cummings, l. G., Distribution of Influenza by Indirect ContactHands and Eating Utensils, American Journal of Public Health 9:25-38, 1919). Of course,'the greater the number of bacteria which remain on tableware in a live condition following the washing operation, the greater the danger of spreading infection. However, a thorough cleaning of tableware such as can be performed by correct loading and operation of a typical household electric dish washing machine will reduce the bacterial count on the tableware to acceptably safe levels. On the other hand, loading or other errors on the part of the operator may somewhat reduce the efiiciency of the cleaning operations. In addition, unless unusual precautions are taken, air borne bacteria may be deposited on tableware while it is in storage following the washing operation.

The ordinary cleaning and drying cycle of a typical household electric dish washing machine is complete in approximately one hour. After this cycle of treating operations is over, the tableware usually remains stored in racks within the machine for severalhours until it is removed for use at the next meal. A common practice with these means is to accumulate'soiled. tableware in the machineduring the day and to wash the complete load just after the evening meal. In this situation, the

Journal of Home Economics, Octotableware may remain in theracks of the machine for i up to 12 hours before reuse. This will occur, for ex ample, when the washing of the tableware is complete at 8:00 pm. and it remains stored in the racks until breakfast at 8:00 a.m.zthe following day.;

a series of rinsing,

In view of the relatively long period during which the tableware remains in a dish washing machine after the washing operation, it is beneficial to provide additional means for sanitizing tableware which will be effective during and following the dish washing operation. Accordingly, I effect this objective by providing a low intensity beta ray source within the cabinet of a dish washing machine. Although beta particles can be employed without extreme precautions because of their low penetrating qualities, they are nevertheless effective to kill bacteria by their disruption of the protoplasm of the bacterial cells. A steel cabinet such as that of a dish washing machinewill more than provide the nominal amount of shielding required for a relatively low con centration of the low energy beta particles. A convenient way to expose tableware to beta rays during treating operations and storage periods in a dish washing machine, is to incorporate a beta ray emission source, such as a radioactive isotope material, into a coating on the storage rack which encloses the tableware. Suitable radioactive isotopes for this application are presently readily obtainable from the Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Accordingly, it is an object of my invention to provide a tableware supporting and storage rack which has inherent sanitizing properties.

Another object of my invention is to provide an improved rack including radioactive beta ray emitting material for supporting, storing, and sanitizing tableware ina dish Washing machine.

A further object of my invention is to provide an improved method of sanitizing soiled tableware including a washing. operation followed by a prolonged exposure of the tableware to the sterilizing effects of low level beta radiation.

A still further object of my invention is to provide an improved method of sanitizing tableware consisting of subjecting the tableware to low level beta radiation during a series of rinsing and washing operations followed by a prolorigedexposure of the tableware to the sterilizing effects of low level beta radiation. 1

Still another object of storage rack inwhich is incorporated beta ray emitting material so that articles placed within the storage rack are made more sterile by being exposed to the beta rays emitted'from the rack.

Briefly stated, in accordance with the illustrated embodiments of my invention,-

I have provided an improved washing and storage rack, which can be used for tableware, consistingof an' -interwoven network of wire cross members. Incorporated in the usual plastic coating on the cross members is, a uniformly distributed, low concentration of a radioactive isotope, such as carbon-14.-

' The carbon-l4 emits-beta rays which willbe dispersed in allditeotioiis 'frornf the storage rack cross members. Tableware disposed within the rack. will accordingly be exposed-tea continuous radiation of beta particles, and through prolonged exposure, thegrowth of bacterial or ganisms on thetableware'will'befiinhibited. a

In another illustrated embodiment of my invention, I employ a deposition of radioactive nickel-63cm the storage rack wire cross members as the emission source of betarays. U v

. As illustrated, the radioactive tableware storage rack of mylin'v'ention is 'conveme'nuyaus d' Within the, tub of an electrically operated householddish washing machine.

However, it may advantageously be used elsewhere for sanitizing, as in anordin'ary kitchen cabinet, w

f It is apparent that' myinvention providesan improved method of sanitizing tableware, including aprolonged erposure of'the tableware' -to beta recons dering andafter Washing, and drying operations carried my invention is to provide .a-

out within the cabinet of an electrically operated dish washing machine.

The subject matter which I regard as my invention is particularly pointed out in the concluding portion of this specification. My invention, however, both as to organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken inconnection with the accompanying drawings in which:

Fig. l is a fragmentary front elevation of a dish washing machine having my tableware supporting and storage rack invention with the cabinet and door partially broken away;

Fig. 2 is an enlarged perspective view of a fragment of the upper tableware rack of Fig. 1; V

Fig. 3 is an enlarged perspective view of a fragment of the lower tableware rack of Fig. l; V

Fig. 4 is an enlarged fragment of the upper tableware rack of Fig. 1 with a portion of one of the rack members illustrating the interior construction;

Fig. 5 is a greatly enlarged sectional fragment of a rack member in perspective illustrating the rack coating of my invention;

Fig. 6 is an enlarged fragment of a tableware rack detail similar to Fig. 4 showing a modified rack structure which may be employed.

Referring now to the drawings, in Fig. l, I have shown my invention incorporated in an electrically operated dish washing machine 1 of the domestic type. The dish washing machine 1 may include a suitably mounted, open front steel tub 2 enclosed within a steel cabinet 3. The

cabinet 3 is provided with a watertight steel door 4,

which is mounted so as to swing outward from a vertical closed position about transverse hinges (not shown) along its lower edge 5, to a horizontal open position. The inside of the door 4 contains a detergent dispenser (not shown) which automatically dispenses a quantity of detergent into the tub during washing operations; This dispenser may be the one shown in I. C. Sharp et al., Reissue 24,198, August 21, 1956, assigned to my assignee.

Within the tub 2 is a revolving-arm treating liquid distributor 6 suitably supported on a hub 7. The distributor 6 is provided with a series of angularly disposed nozzles 8 to distributethe treating liquid under suitable pressure. Distributor 6 is rotated by the jet reaction of the treating liquid issuing from the nozzles 8 under the pressure generated by the centrifugal recirculating pump 10, which is driven by the motor 11. To facilitate drying of the tableware there is mounted to' the hottomof tub 2 a sheathtype electrical resistance heating'unit 12., ,Also within the bottom of the tub isa drain opening cover 13 below which is a filter housing 14. As the filter "within the housing 14 forms no part of this invention, its description has been omitted for the sake of brevity. Depending from the filter housing is an inlet hose 15 leading to the pump 10. The discharge outlet 16 of pump 10 is connected to the pipe fitting 17,1nourited below the distributor hub 7. Alsodependingifrom'the housing 14 is an inlet hose 18 leading to'fa discharge pump.20 driven by a motor 21. Leading from the dis- "charge pump 20 is a discharge hose 22 which may be connected to the drain system of a house in which the dish washer 1 may be operating.

Water is supplied to the tub 2 th-roughthe inlet'opening 23 supplied by a water inlet tube 24 under control of a suitable electrically operated water inlet valve 25.. The

inlet valve 25 is connected toa hot watersource through hose 26 so that water of suitable temperature may be admitted to the tub.

Within the top part of the tub 2 is an upper tableware rack 27 which is mounted on suitable rollers 28 which travel on horizontal tracks 29. The upper rack 27 is adapted to support glasses 30, cups 31 and similar. articles on its longitudinal and transverse members32 and33'.

during and after the washing operations. The longitudinal and transverse members are relatively closely spaced so as to be in close proximity to all surfaces of tableware within the rack.

Within the lower part of the tub is a lower rack 34 which is mounted within the tub substantially the same as upper rack 27. Lower rack 34 is adapted to support larger dishes 35, silverware 36 and similar articles during and after the washing operations. The dishes 36 lie against the sinuous upright supports 37 during and after the washing operations. As shown, the supports 37 are formed in a slightly convex fashion so as to provide intimate contact with the inside of the dishes 36.

A typical construction for tableware racks includes a network of steel wire cross members over which is ap plied a coating of resilient, polyvinyl chloride type plastic material measuring between and in thickness to cushion fragile articles of tableware. Application of this coating may be advantageously carried out by means of a suitable dipping tank. In a preferred embodirnent of my invention, I uniformly disperse a predetermined quantity of radioactive carbon-l4 isotope into the polyvinyl chloride plastic coating material before it is applied to the steel Wire rack. I prefer to use carbon-14, because in addition to being readily available, it is an eflicient source of beta radiations with an energy of 0.155 million electron volts and with a half-life of 5,568 years. Also, it emits none of the relatively hazardous gamma rays. The beta particles emitted by the carbon-l4 under ideal conditions will travel approximately 28 centimeters through air, a range which is more than adequate for sterilizing contact with all surfaces of tableware in the tableware rack of my invention. Moreover, the beta particles emitted by the carbon-14 are relatively safe to employ for sanitizing as in a dish washing machine because they are easily shielded. For example, beta particles emitted from carbon-l4, at the maximum, will travel only approximately 0.004 centimeters or less than 0.002 inch through steel as used in a dish washing machine. As a typical domestic dish washing machine tub consists of 0.044. inch steel encased in three layers of porcelain enamel and frequently also enclosed in a cabinet with 0.030 inch steel walls, it is readily apparent that the shielding present ina dish washing machine is more than sufiicient to prevent the escape of any harmful carbon-l4 beta radiation.

The radioactive carbon-l4 is obtainable in a solid barium carbonate form from the Oak Ridge National Laboratory at Oak Ridge, Tennessee: Barium carbonate including the carbon-l4 isotope may be finely divided and thoroughly mixed into the polyvinyl chloride plastic material used for coating the racks.- The amount of the carbon-l4 isotope material that is mixed into the coating is afunction of the geometry of the storage rack, the level of radiation desirable for efficient sanitization, and the maximum radiation compatible with adequate safety conditions in normal domestic usage. The amount of coating on the racks wire cross members and the surface area of the complete coated rack can be geometrically determined. Also, a desirable level of radiation at the rack-surface may be chosen based on efficient sanitization and adequate safety conditions in the application. Then a calculation maybe made of the amount of radio active carbon- 14 isotope material to mix into the plastic coating'material'for the desired radiation level using the measured radioactivity concentration for an available form of the radioactive isotope; For example, the cur rent Radioisotopes catalog of the Oak Ridge National Laboratory discloses that radioactive carbon-l4 is a stock, item in the formv ofsolid BaCO 'with a radioactivity concentrationbetween 9 an d millicuries'per gramof. BaCO The calculated results may then be tested by an experimental application on 'a' sample tableware rack. The radiation level obtained with the experimental rack can then be easily-checked with a particle counter. Next, the calculated amount required can be adjusted to agree with the actual results obtained as shown by the particle counter. The data thus provided can then be applied to pilot run and later production run quantities. Of course, the radiationlevel of tableware rack coatings must be constantly checked and carefully controlled during-regular production for desired results and maximum safety.

I prefer to use a concentration of carbon-14 in the rack coating sufficient to provide an emission of'radiant energy within a range extending from 60 to 100 milliroentgens per hour radiating from the surface of the tableware rack. This amount of radiation, although at a relatively low level, provides adequate supplemental sanitization of the tableware in view of the fact that the tableware is relatively well sanitized by the washing and rising operations in the dish washing machine and is exposed to the beta particle emission for a substantial period of time ranging between three and twelve hours. This level of radiation is not dangerous to a house wife who may be using a dish washing machine including my tableware rack invention because she is only loading and unloading the dish washing machine for a very few minutes a day. However, it will be understood that the radiant energy level specified herein applies particularly to my preferred embodiment and the conditions normally associated with its use. Sanitization by beta irradiation is a function of the length of time the article being sanitized is exposed to the radiations and the energy level of the irradiation. Thus, assuming a given exposure period and radiation energy level, a longer exposure period at a lower energy level rate can provide the same degree of sanitization. correspondingly, a higher radiation energy level for a shorter exposure period may also provide the same degree of sanitization.

In order to improve the efficiency of the radioactive material present in myrack coating, I have found it beneficial to apply the radioactive material close to the outer surface of the rack members. This is desirable because the plastic coating itself will obstruct the easily shielded beta particles. Therefore, only particles at or near the surface of the rack members have the most desirable sanitizing effectiveness. The rack may first be coated with a thin layer of ordinary polyvinyl chloride plastic containing no radioactive material, and then given a second and outer coating of plastic containing the radioactive carbon-l4 isotope. This procedure is economical in that it uses less of the radioactive material and provides the same efiicient beta ray emitter because most of the activity is derived from the radioactive particles that are at or near the surface of the rack members. This construction is best illustrated in Figs. 4 and 5, in which the steel wire forming the base of the rack is designated by number 38. The coating on the Wire 38 is generally shown as number 40. As shown, the coating 43 contains minute particles of beta ray emitting carbon-l4 isotope designated by number 41. Fig. 5 illustrates the dispersion of the radio isotope particles 41 so that they are close to the surfaces of the rack coating, thereby increasing the average energy level of the radiations.

The operations of the dish Washing machine I are automatically controlled through the manipulation of a control knob 39 which actuates a program controller (not shown). The program controller is of a Well known type which includes a plurality of switch actuating cams on a shaft, driven by a timer motor and an escapement mechanism, such as that shown in D. F. Illian Patent 2,668,589, issued February 9, 1954, and assigned to my.

assignee.

My storage rack-invention will best be understood in connection with the following description of its use in the dish washing machinel. Atthe conclusion of a tends until the tableware is the door 4 is then closed and the control knob 39 is turned to an on position. The machine. will then automatically proceed through a complete cycle of tableware sanitizing operations.

The initial operation consists of a pre-rinse in which food particles are loosened by a pressurized water rinse and flushed down the drain before washing of the tableware actually starts. 'After the pre-rinse operation, the controller of the machine actuates one or more washing operations carried out on the tableware in which pressurized water, to which detergent has been automatically added by the dispenser, washes away substantially all traces of food soil from the tableware. When the washing operation is, concluded, the tableware may be exposed to one or more rinsing opera-tions using waterto which a small amount of rinsing agent may be added. Following the last rinse, the tableware undergoes a drying operation in which a heating unit such as electrical heating unit 12 may be used to heat the air within the cabinet to facilitate drying. It will be understood that during all of these operations the tableware is also being subjected to low level beta irradiation from the tableware racks 27 and 34. After the dryingoperation is complete, the electrical dish washing mechanism'shuts off automatically and the tableware. is exposed to low level betal radiation for a relatively long period which exremoved from the storage racks. As illustrated, the construction of the tableware racks is such that articles stored within the racks are completely surrounded by the rack members so that all surfaces of the tableware are exposed to the sanitizing radiations from the rack members. The close spacing of the rack cross-members and their disposition so as to be intimate relation with easily contaminated portions of the tableware such as the rims of glasses and the inside of dishes insure that any residual bacteria on the tableware will be subjected to the sterilizing effects of the beta rays. The continuous irradiation will, of course, render harmless any bacterial organisms remaining on the tableware after the last rinsing operation or that may fall on the tableware during the storage period. As described hereinbefore, my invention provides a positive and effective means and method of removing t'ood soil and harmful bacterial organisms from tableware resulting in improved sanitization of the tableware.

Fig. 6 illustrates a modification of my invention coni sisting of a tableware rack 42 constructed from steel wire 43 on which is deposited a plating 44 which includes a predetermined quantity of beta ray emitting nickel-63 isotope. Nickel-63 can be used advantageously to provide a beta ray source suitable for application to tableware storage racks. It has a half-life of 85 years. As to radiation, it emits no gamma particles, and has a beta ray energy emission equalto 0.067 million electron volts. This isotope material is presently available from the Oak Ridge National Laboratory, at Oak Ridge, Tennessee in the form of a nickel-chloride solution. The nickel-63 can'be deposited on the tableware washing and storage.

racks by the use of standard electrodeposition procedures. The calculation of the quantities required may be similar to that explained above in connection with the carbon-14 embodiment. It will be understood that my invention is not limited to the use of the two radioactive isotope exmeal, soiled table ware such as glasses, dishes, cups, and

silverware are removed from the table and placed within the storage racks 27 and 34-of the dish washing machine 1. Detergent is placed in the detergent dispenser and amples particularly described herein.

While there has been described what is at present con- 7 sidered to be the preferred embodiments of the'invention, it will be understood that various modifications-may be made therein, and it is intended tocover in the appended claims all such modifications as fall within thescope of the invention.. I l

I claim:

l. In a tableware washing machine of 'the type having a cabinet with an access opening, a control system for actuating tableware washing and drying operations, atub within said cabinet, means to'intro'duce and distribute V washing liquids within said tub, and means to remove said liquids and soil fromsaid machine, the improvement comprising; a tableware rack having a multiplicity of beta ray emitting structural members for supporting said tableware during said operations within said machine, said rack disposing said beta ray emitting members in positions whereby substantially all surfaces of said tableware from which foods are eaten or drunk are within the transmission range of said beta rays and, therefore, are exposed to direct contact by said beta rays, thereby rendering harmless organisms on the surfaces of said tableware.

2. In a machine for removing food soil from tableware the combination comprising: a cabinet having an access opening provided with a door; a tub within said cabinet; means to introduce treating liquids into said tub; means to distribute treating liquids within said tub to rinse and wash said tableware; means to drain treatingliquids and food soil from said tub; air heating means within said tub. to dry said tableware after its exposure to treating liquids; and an open structured wire rack disposed within said tub for containing tableware during and after treating operations within said machine, said rack consisting of a multiplicity of structural members for supporting said tableware in close proximity to the surfaces thereof, said structural members having an exterior coating containing a substantially uniformly dispersed quantity of radioactive material emitting beta rays, whereby the surfaces of tableware disposed within said machine are exposed to said eta rays thereby rendering harmless bacteria on said surfaces.

3. In a machine for carrying out a series of treating operations to sanitize soiled tableware the combination comprising: a cabinet having an access opening provided with a door; a tub within said cabinet; means to introduce treating liquids into said tub; means to distribute treating liquids within sad tub and thereby to remove food soil from said tableware; means to drain treating liquids and food soil from said tub; air heating means within said tub to dry said tableware after its exposure to treating liquids; and a rack having an access opening disposed within said tub for supporting and storing tableware during and'after liquid treating operations within said ma chine, said rack consisting of a multiplicity of members closely distributed around the surfaces of tableware being supported within said rack, said tableware supporting members containing adjacent the outer surface thereof a of material containing a uniformly dispersed quantity of radioactive isotope emitting beta radiations, whereby the surfaces of dishes withinthe rack, and in particular the inside surfaces of said dishes, are in intimate relationship with a plurality of beta ray sources on said rack members so that bacterial organisms on said dishes will be exposed to said beta irradiation, and thereby be rendered harmless.

6. An open structured wire rack for supporting and sanitizing glasses and cups consisting of a network of cross-members comprising: an open base with support positions for the rims of said glasses and cups, each of radioactive isotope material emitting only "beta rays,

whereby substantially all surfaces of tableware disposed within said machine are exposed torsaid beta rays thereby rendering harmless any bacteria remaining on the surfaces of said tableware after said liquid treating operations 'within said machine; I

4. A dish washing machine comprising, in combination; a tub having an access opening, a closure for said tub, said tub and closure being impervious to the passage of beta rays, rack means within said tub for supporting a plurality of articles of tableware to be washed, s'aidrack means comprising a multiplicity of beta ray emitting membersengageable with said articles of tableware to dispose substantially all surfaces of said tableware in, close proximity to said beta ray 'emitting rnembers, means for subjecting said tableware to the action of Washing and rinsing liquids, means for removing said liquids from said tub, and means for drying said articles of tableware without removing the same from said rack means.

5; An open structured rack for'supporting and sanitizing dishes comprising: an open structured base with support positions for-the lower edges of dishes, upright members consisting of a multiplicityof loops formed in substantially convex fashion extending angularly upwardly from said base, whereby the concave inside of dishes disposed within said support positions will lie substantially against said convex upright members'gjaccessi openings for said' supportpos itions withinsaid-racband b n the exterior b'fsaid'base and support members a layer said support positions including a plurality of closely spaced cross-members, whereby substantially all portions of the rims of glasses and cups disposed within said support positions will lie upon or be immediately adjacent said cross-members; access openings for said support positions within said rack; and on the exterior of said cross members a layer of material containing a uniformly dispersed quantity of a radioactive isotope emitting beta radiations, whereby the surfaces of glasses and cups, and in particular the rims of glasses and cups within the rack, are in intimate relationship with a plurality of beta ray sources on said rack cross-members so that bacterial organisms on said glasses and cups will be exposed to said beta irradiation, and thereby be rendered harmless.

7. A rack for supporting a plurality of articles of tableware within an enclosure resistant to the passage of beta rays, comprising an openwork structure having elements forming a reticulated base, a plurality of members extending transversely thereof in spaced relation therewith and a plurality of members extending upwardly therefrom, said base and said transversely and upwardly extending members collectively providing means for supporting said tablewarearticles in relatively close mutually spaced relation separated by said transversely and said upwardly extending members, certain of said tableware supporting members extending transversely of the surfaces of said tableware from which food is eaten and no .part of said last named supporting members being more than 28 centimeters from said surfaces, and all of said tableware supporting means having a coating of resilient material embodying in at least the outer layer thereof, a substantially uniformly distributed beta ray emissive material having a transmission range through air of at least 28 centimeters.

8. A wire rack for supporting tableware following the washing thereof, comprising: an open'structured network of closely distributed longitudinal, cross, and upright members comprising support elements for said tableware; and upon said network of members a coating of material containing a uniformly dispersed quantity of radioactive carbon-14 isotope providing an emission source of-beta rays whereby substantially all surfaces of tableware being supported within said rack 'are exposed to said beta rays thereby rendering harmless bacterial organisms disposed upon said surfaces.

9. A wire rack for. supporting and storing tableware within an enclosing structure such as a dish washing machine comprising: means providing an open structured ,network of closely distributed longitudinal, cross, and upright members for supporting said tableware; and upon said network of members a coating of material containing a uniformly dispersed quantity of radioactive nickel-63 isotope providing an emission source of beta rays whereby substantially all surfaces of tableware being supported within said rack areexposed to saidibeta rays thereby rendering harmless bacterial organisms disposed upon said surfaces; N

, 1Q. A wire rack for supporting and storing tableware within a dish washing machine, said rack havingan access opening and consisting of an open structured network of cross me'mbers providing support places for tableware articles, said cross members engaging and being" otherwise 9 10 in close proximity to the surfaces of tableware supported References Cited in the file of this patent within said rack; and upon said rack members a coating UNITED STATES PATENTS of material containing a radioactive isotope emission 2 095 502 Johnston Oct 12 1937 source of beta rays having an energy level range between 2403526 Harris Jul'y 1946 60 and 100 milliroentgens per hour, whereby substantially 5 2:446:693

Davis Aug. 10, 1948 all surfaces of tableware w1th1n 581d rack are exposed to 2,484,782 Copley Oct 11 1949 the action of said beta rays, thereby inhibiting bacterial 2,721,661 W lf Oct 25, 1955 growth on said tableware. 2,804,213 Fox Aug. 27, 1957 

